The invention relates to a process and an apparatus for comminuting, dispersing, desagglomerating and/or mixing flowable material in chemical industry, ink making industry, textile industry, pharmaceutical industry, cosmetic industry and food industry. Particularly, e.g., dispersing and/or desagglomerating of ink pigments or blending of plastic material.
Devices known heretofore for carrying out the procedures mentioned above relate mainly to mills having rotary components, such as agitator mills, roller mills or other devices where shearing forces basically act upon the particles to be treated.
Likewise, inflow technique processes are known (see E. J. Windhab: xe2x80x9cInflow Technique Processes for Producing Functional Structures in Multiphase Food Systemsxe2x80x9d, Lebensmittel-Technologie 29/No. 4/96). By a combination of thermal and mechanical stress of multiphase fluid systems, a specific production or alteration of disperse structures can be achieved in well-defined flow fields (e.g., shearing flows).
Investigations have confirmed that, apart from shearing flows, expansion flows can also be used for treating the materials corresponding to the above applications [see Reichert, thesis 1973, University of Karlsruhe as well as Manas-Zloczower and D. L. Feke, International Polymer Processing IV(1989), pp. 3-8 ]. It has been shown that, apart from a shearing flow, further forms of flow, such as expansion flows, exist which are considerable more effective as to specific energy and time of treatment.
Expansion flows have already been used earlier. GB-A-2,039,225 discloses a succession of nozzles of converging and then enlarging cross-sections. It is shown that particles flowing through the converging section are laterally compressed and expand in length up to the moment where the particles pass the smallest cross-section of the nozzle and are torn into fines. The use of nozzles, however, compresses the particles from all sides so that the particles expand in one dimension only, i.e., in length. Therefore, to achieve proper comminution, a series of nozzles is necessary. Moreover, since nozzles have a very limited cross-section, the quantity of fluid passing through per time unit is very much restricted so that this nozzle arrangement has not found any acceptance on the market due to its reduced efficiency.
Therefore, the present invention provides a process and an apparatus which mainly use expansion forces for treating, particularly comminuting, dispersing, disagglomerating and/or mixing, flowable materials where the material is treated in a more efficient manner. In particular, the apparatus does not require moving components.
According to the invention, the problem is solved by a process in which the material is almost exclusively subjected to two-dimensional expansion forces within a stream. xe2x80x9cTwo-dimensionalxe2x80x9d refers to expansion both in length and in width. In this way, seemingly a double effect is achieved, but in reality the comminution effect is multiplied so that an apparatus according to the invention can be very much simplified, nevertheless working more efficiently and allowing a considerable throughput.
In practice, the above problem may be solved by an apparatus, called a xe2x80x9cgap mill,xe2x80x9d for reducing the size of particles of a flowable material in a streaming fluid. According to the present invention, the apparatus includes a pressurizing device, such as at least one of a compressor (for air and gases) or a pump (for liquids) which feeds the fluid under pressure together with the particles through an inlet into an open space. This space is only confined by a pair of opposing wall surfaces delimiting the space. These wall surfaces are narrowing to each other up to a gap of smallest cross-section An outlet communicates with the gap to discharge the fluid which then contains the particles in comminuted, dispersed, desagglomerated and mixed form.
Such a mill according to the invention does not necessarily include any movable component except for the conveying elements, such as a pump. The desired tension condition within the stream is achieved in that the product is pressed through a converging gap of the mill. In the course of this, the power required has to be raised in form of pumping power. Investigations have shown that the stress on agglomerates are comparable with that within the roll gap of a roller mill with respect to tension level, number of stressing and specific energy.
The walls of the mill can be in the form of base bodies which are substantially conical of a predetermined maximum radius wherein the inlet is radially outwards, while the outlet is radially inwards and the constriction and gap is in the center. Of course, this arrangement could be inverted by providing two hollow cones with the inlet in the center, while the outlet and the gap are radially outwards, but this is not preferred.
The gap mills according to the invention can be combined in a process with agitator mills, roller mills or similar devices known per se by preponing, interposing and/or postponing them.
According to an aspect of the present invention, an apparatus for at least one of comminuting, dispersing, desagglomerating and mixing flowing material is provided. The apparatus includes a gap mill having a pair of cylindrical frustro conical shaped base bodies with a wide base surface and a truncated conical end, wherein each base body has an axially centered bore. The frustro conical shaped bodies are positioned so that the bores of the bodies are axially aligned, and form a thin gap between the truncated conical ends of the base bodies. An annular space is defined between the pair of base bodies of the gap mill.
According to another aspect of the present invention, the annular space has a cross-sectional shape of two funnels connected together at their spout ends. In another aspect of the present invention, the annular space has a cross-sectional shape of a hyperbola.
According to a further aspect of the present invention, the apparatus includes an outer jacket connected to the wide base surfaces of the pair of cylindrical frustro conical shaped base bodies arranged to enclose the annular space. At least one inlet bore penetrates through the outer jacket, wherein the flowing material enters said at least one inlet bore, flows through the annular space, enters said axially centered bores via the thin gap, and exits through one of said axially centered bores.
In another aspect of the present invention, a plurality of the gap mills are stacked together forming a xe2x80x9cparallel connectionxe2x80x9d gap mill. The xe2x80x9cparallel connectionxe2x80x9d gap mill includes a plurality of axially centered bores axially aligned to form a central xe2x80x9cseriesxe2x80x9d bore having two main outlet exits. Each of the plurality of gap mills include an annular space. At least two xe2x80x9cseriesxe2x80x9d inlet bores including a plurality of inlet bores, each at least one inlet bore is coupled to each annular space.
According to a still further aspect of the present invention, the apparatus further includes at least one supply container and at least one pump arranged to form a closed-loop flow path such that the flow material continuously flows through the pump, the gap mill, and the supply.
In yet another aspect of the present invention, at least one supply container connected to a plurality of gap mills which are arranged so that said axially centered bores are axially aligned. A pump is arranged upstream of each gap mill and a receiving container connected to the outermost the axially centered bores of the plurality of gap mills.
According to a further aspect of the invention an apparatus for at least one of comminuting, dispersing, desagglomerating and mixing flowing material is provided. The apparatus includes a cylindrical frustro conical shaped body having a wide base surface, truncated conical end, an axially centered bore; and a planar body. The cylindrical frustro conical shaped body and the planar body are arranged to form an annular space, and a thin gap between the truncated conical end and the planar body.
Other exemplary embodiments and advantages of the present invention may be ascertained by reviewing the present disclosure and the accompanying drawing.